package dataStructQueue;

import java.util.LinkedList;
import java.util.Queue;

public class MyStack {
    //  用队列实现栈
    private Queue<Integer> queue1;
    private Queue<Integer> queue2;

    public MyStack() {
        queue1 = new LinkedList<>();
        queue2 = new LinkedList<>();
    }

    public void push(int x) {
        if(empty()){
            queue1.offer(x);
        } else if (queue1.isEmpty()) {
            queue2.offer(x);
        } else if (queue2.isEmpty()) {
            queue1.offer(x);
        }
    }

    public int pop() {
        if(empty()){
            return -1;
        }
        if ( !queue1.isEmpty()) {
            int size = queue1.size();
            for (int i = 0; i < size-1; i++) {
                int val = queue1.poll();
                queue2.offer(val);
            }
            return queue1.poll();
        } else {
            int size = queue2.size();
            for (int i = 0; i < size-1; i++) {
                int val = queue2.poll();
                queue1.offer(val);
            }
            return queue2.poll();
        }
    }

    public int top() {
        if(empty()){
            return -1;
        }
        if ( !queue1.isEmpty()) {
            int size = queue1.size();
            int val = -1;
            for (int i = 0; i < size; i++) {
                val = queue1.poll();
                queue2.offer(val);
            }
            return val;
        } else {
            int size = queue2.size();
            int val = -1;
            for (int i = 0; i < size; i++) {
                val = queue2.poll();
                queue1.offer(val);
            }
            return val;
        }
    }

    public boolean empty() {
        if(queue1.isEmpty() && queue2.isEmpty()){
            return true;
        }
        return false;
    }


}
